Anesthesia Considerations in Patients Undergoing Spine Surgery with Evoked Potential Monitoring

Abstract

Intra-operative neuromonitoring (IONM) facilitates monitoring of the functional integrity of neural structures under general anesthesia. It aids in early detection of injury and minimizes postoperative neurologic deficit. IONM may be used during spine surgery, where either the blood supply to the spinal cord could be compromised or the surgical procedures where there is manipulation of the spinal cord. Somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) are used to monitor the sensory and motor tracts in the spinal cord, respectively. Preoperatively, a team of surgeons, anesthetists, and neurophysiologists must discuss about modalities of IONM to be used, expected changes, and alarm criteria. Anesthesia drugs need to be appropriately selected to facilitate IONM, as they affect the SSEP and MEP response obtained. Both total intravenous anesthesia and balanced anesthesia technique may be used, with appropriate titration of drugs. False-positive changes in evoked potentials (EPs) must be prevented by a steady anesthesia state and physiologic parameters. It is preferable to have a checklist to follow whenever changes in EP response are observed to rule out surgical, anesthetic, and monitoring-related causes for change in response. Risk–benefit must be assessed before the selection of a patient for EP monitoring as it may be rarely associated with complications such as burns, seizures, and bite injuries to lips, tongue, and endotracheal tube. Teamwork with meticulous planning, preparation, and multidisciplinary communication is essential for the safe conduct of spine surgeries with SSEP and MEP monitoring. In this review, we discuss various considerations for anesthesia management in patients with intraoperative EP monitoring.